Evaluating Water Quality in a Large River System in the Northern European Russia by Macrozoobenthos

Macrozoobenthos analyses were used to evaluate the ecological water quality in the Shuya River, a large tributary of Onega Lake, which determines water chemistry in the water intake of Petrozavodsk City, the capital of the Republic of Karelia. Water quality indices, widely used in the world practice, were applied, including FBI, EBI, BMWP, ASPT, BBI, IBGN, GW, EPT, and IM, as well as the integral IBC index. At the average estimate good, the values of indices showed a strong dependence on the characteristics of the station. Samples taken in pool areas with soft soils gave underestimates of water quality indices. The quality classes moderate and good was found in small tributaries, and the quality class excellent, in rapids in the lower reaches of large rivers. It is recommended to evaluate water quality separately for pool areas, small tributaries, and rapids in the main channel; the obtained indices are recommended only to compare similar biotopes. The river ecosystem was found to be in a stable state, comparable with that in the 1980s, notwithstanding the heavier anthropogenic load.